The specific aims of the study are: 1) to describe the effects of streptokinase therapy (STK) postmortem on the morphology of the myocardium after acute myocardial infarction; 2) to compare the infarct size, postmortem, in patients with acute myecardial infarction who received STK therapy versus those who received conventional therapy (controls); 3) to describe the transmural progression of cell death after acute myocardial infarction; 4) to describe and measure the thrombolytic effects of STK therapy on the residual percent occlusion of artherosclerotic coronary arteries after acute coronary thrombosis; and 5) to compare the infarct size estimated by a validated reliable electrocardiographic variable, the integral of the vector spatial magnitude during initial abnormal depolarization (IAD) in patients who survived acute myocardial infarction and who received streptokinase therapy versus those who received conventional therapy. Evidence from experimental animal studies suggest that coronary artery reperfusion in the early hours after the onset of myocardial infarction can interrupt, and possibly prevent irreversible myocardial necrosis. Thrombolysis can be achieved in 70%-80% of patients by the intracoronary administration of streptokinase. It is probably of major benefit to reduce infarct size only when it is applied within the first three hours after the onset of symptoms of infarction. The proposed study may be the first prospective, large, controlled pathological analysis of the effects of streptokinase on the evolving infarct and residual coronary stenosis in man. Approximately 114 patients will be studied postmortem. Pathological analysis of the myocardium will include: incubation in nitroblue tetrazolium; volume measurement by displacement, histochemistry, and planimetry. Pathological analysis of the coronary arteries will include: angiography, histochemistry, and planimetry. Vectorcardiographic analysis will be done by computer.